NEW TGB(A) SERIES EXHIBITING A S(C)ASTERISK-S(A)S(A)ASTERISK-N-ASTERISK PHASE SEQUENCE

A new series with a chiral tolane core has been synthesized. These materials belong to the optically active series: 3-fluoro-4-[(R) or (S)-1-methylheptyloxy]4'-(4"-alkyloxy-3"-fluorobenzoyloxy)tolanes (nFBTFO1M7). For the first time, the helical S(A)* phase or TGB(A) phase is found in all of the derivatives from heptyloxy to octadecyloxy. The S(A)-S(A)*-N* phase sequence is observed in several compounds with short chains and the S(C)*-S(A)-S(A)*-N* phase sequence is obtained with the decyloxy derivative. The TGB(A) phase has filament or cholesteric textures. The helical pitch of the TGB(A) phase is short for the octadecyloxy derivative and is compared with that for different chain lengths as a function of temperature. The layer spacing in the TGB(A) phase shows that it is incommensurate with the fully elongated molecular length.